Scientists have long debated whether dinosaurs were in decline before an asteroid struck the Earth 66 million years ago, causing a mass extinction. New research suggests that dinosaur populations were still thriving in North America before the asteroid impact. However, independent experts caution that this is only one piece of the global picture.
“Dinosaurs were quite diverse, and now we know there were quite distinct communities roaming around before being abruptly wiped out,” said Daniel Peppe, a study co-author and paleontologist at Baylor University.
The latest evidence comes from analyzing a portion of the Kirtland Formation in northern New Mexico, a site known for around 100 years to contain several interesting dinosaur fossils. Scientists now say those fossils and the surrounding rocks date from about 400,000 years before the asteroid struck—considered a short interval in geologic time.
The age was determined by analyzing small particles of volcanic glass within sandstone and by studying the direction of magnetic minerals within mudstone of the rock formation. The results indicate that “the animals deposited here must have been living close to the end of the Cretaceous,” the last dinosaur era, Peppe said.
These findings were published Thursday in the journal *Science*.
Differences between the dinosaur species found in New Mexico and those discovered at a site in Montana, previously dated to the same time frame, “run counter to the idea that dinosaurs were in decline,” Peppe explained. The fossils found at the New Mexico site include *Tyrannosaurus rex*, a huge carnivorous dinosaur, and a Triceratops-like horned herbivore.
Scientists who were not involved in the study have urged caution in interpreting these results. “This new evidence about these very late-surviving dinosaurs in New Mexico is very exciting,” said Mike Benton, a paleontologist at the University of Bristol. However, he added, “This is just one location, not a representation of the complexity of dinosaur faunas at the time all over North America or all over the world.”
Although dinosaur fossils have been found on every continent, accurately dating them remains challenging, said paleontologist and study co-author Andrew Flynn of New Mexico State University. Since easily datable materials such as carbon do not survive in fossils, scientists must rely on surrounding rocks with specific characteristics to determine their age.
Further research may help complete the picture of the range of dinosaur species alive globally on the eve of the asteroid impact, Flynn noted.
https://nypost.com/2025/10/24/us-news/dinosaurs-thrived-in-north-america-before-the-mass-extinction-asteroid-strike-new-study-shows/